If work is leaving you drained, try turning off your smartphone at lunchtime.
A study found that those who played on their phone during their lunch break were more tired during the afternoon than those who went for a walk or read a book.
This may be because they used up more mental energy - or simply because their eyes were strained or their necks were cricked.
The South Korean researchers said workers should be aware of the effect and employers should consider introducing "digital detoxes".
For the study, some 425 men and women were asked how they spent their lunch break and how they felt at the time and afterwards.